The Digital Subscriber Line (DSL) network architecture is evolving from the Point to Point Protocol over Asynchronous Transfer Mode (PPP over ATM) to an enabling architecture of IP Quality of Service (QoS) based on Ethernet aggregation and connection. Under this background, a general reference architecture of the DSL is illustrated in FIG. 1.
In the DSL reference architecture as illustrated in FIG. 1, T is a reference point between a User Equipment (UE) and a Residential Gateway (RG) in a Customer Premises Network (CPN); U is a reference point between an RG and an Access Node (AN, i.e., DSL Access Multiplexer, DSLAM); in an Access Network (AN), there is an Aggregation Network between the AN (i.e., the DSLAM) and a Broadband Remote Access Server (BRAS) or a Broadband Network Gateway (BNG); V is an Ethernet Aggregation reference point between the AN (i.e., DSLAM) and the BRAS/BNG in the access network; A10 is a reference point between the access network and a Service Provider (SP). The reference point A10 may connect an Application Service Provider (ASP) to a Network Service Provider (NSP) including an access network, or connect the NSP to an access network in a visiting area in the scenario of roaming. The CPN is connected with the access network in a DSL access technique. For a Passive Optical Network (PON), the AN is an Optical Line Termination (OLT), and the CPN is connected with the access network in a PON access technique, etc.
At present, as illustrated in the DSL reference architecture of FIG. 1, there is no reference point between ANs (i.e., DSLAMs) of the DSL network, and only star or tree networking can be adopted between the ANs (i.e., DSLAMs) and the BRAS/BNG of the DSL network. In the procedure of attempting to achieve the present invention, the inventor finds that the DSL reference architecture of FIG. 1 has at least the following disadvantages:
1. For providing multicast services such as IP TV, the BRAS/BNG and the aggregation network should support multicast copy, thereby the existing DSL network should be modified. A schematic diagram of a multicast and broadcast model of a DSL network with star or tree networking is illustrated in FIG. 2. Because star or tree networking paths (BNG->AN1, BNG->AN2, BNG->AN3, . . . , BNG->ANn) are adopted to transmit multicast or broadcast data streams, which results in a large amount of multicast or broadcast traffic in the DSL network.
2. If a network single point of failure occurs in the connection between an AN and the BRAS/BNG as illustrated in FIG. 3, the AN disconnects with the BRAS/BNG, and all users connected to the AN are provided with service.
3. The traffic between users covered by different ANs should be transferred by the BRAS/BNG. A path for communication between users covered by different ANs is illustrated in FIG. 4. The path is long with a long delay. The BRAS/BNG becomes a bottleneck for the communication and can not meet the requirements of future VoIP and Peer-to-Peer communications.